698 OCEANOGRAPHY 



might begin with a description of the pond for large breeding indi- 

 viduals, or "parents," and with an account of egg-laying and hatching. 



The "parents' pond" does not differ in any remarkable way 

 from the general plan of a pond given above. Usually one of the 

 largest ponds is chosen, and it can be distinguished from the others, 

 because one or two of its slopes are usually kept up very carefully, 

 while the other slopes, or those of other ponds, are apt to be worn by 

 rain and wind and to become rugged. These well-kept slopes are 

 invariably on the warmer sides, where the sun pours down its mid- 

 summer rays longest, and are carefully worked over in the spring 

 so that the tortoises will find it easy to dig holes in them. In the 

 breeding-season these sides are seen to be covered with wire baskets 

 which mark the places where the eggs have been laid. 



Copulation takes place on the surface of the water in the spring. 

 Egg-deposition begins in the last part of May and continues up to 

 the middle of August. Each female lays during that time two to 

 four deposits, the number differing with individuals and with years. 1 

 The process of egg-deposition is very interesting. A female comes out 

 of the water and wanders about a little while on the banks of the 

 pond in search of a suitable locality in which to deposit eggs. Hav- 

 ing finally chosen a spot, with her head directed up the bank, she 

 firmly implants her outstretched forefeet on the earth, and during 

 the whole operation never moves these. The process of egg-deposi- 

 tion, which takes altogether about twenty minutes, may be divided 

 into three portions, occupying about the same length of time, namely : 

 (1) digging a hole, (2) dropping eggs in it, and (3) closing the hole. 

 The digging of the hole is done entirely with the hind legs. Each, 

 with its nails outstretched, is moved firmly from side to side that 

 is, the right foot from right to left and the left from left to right, 

 and the two are worked in a regular alternation, while the body is 

 swayed a little from side to side, accompanying the motion of the 

 legs. The force put in the lateral pressure of the feet is so strong 

 that the earth that has been dug out is sometimes thrown off to a 

 distance of 10 feet or more, although the largest part of it is heaped 

 up around the hole. Digging seems to be continued as long as there 

 is any earth within the reach of the legs to be brought up. The 

 result is a squarish hole with the angles rounded off, and although 

 its size differs with the size of the female, it is generally about three to 

 four inches across at the entrance, with the depth and width inside 

 about four inches or more. When digging is finished eggs are dropped 

 from the cloaca into the hole, which naturally lies just below it. 

 The eggs are heaped up without any order, but, there being no cha- 

 lazae, the yolk is able to rotate in any direction, and the blastoderm, 



1 See my notes: "How many times does the snapping-turtle lay eggs in one 

 season?" Zoological Magazine, vol. vii, p. 143, 1895, Tokyo. 



